CLAIM FOR BENEFIT OF PRIORITY
Applicants claim benefit of priority under 35 USC 119 based on Japanese Patent Application No. 08-085675 filed on Mar. 14, 1996, the entire disclosure of which, including specification, claims, drawings and summary, is incorporated herein by reference in its entirety.
1. Field of the Invention
This invention relates to a liquid crystal display device, and more particularly to such a device having a touch panel arranged on a liquid crystal display screen.
2. Discussion of the Background
In the prior art, when a touch panel is arranged on the front of a liquid crystal display screen, a gap is provided between the display screen and the touch panel. This prevents irregularities of colors arising from touching of a distorted touch panel to the liquid crystal display screen. However, providing the gap produces an air layer between the display screen and the touch panel, which decreases the transmission rate of light beam, and further reduces the display quality.
To solve these problems, the gap between the touch panel and the lower supporting plate of the display screen is cohered using a transparent double-sided cohesive sheet, which eliminates the air in the gap, as disclosed in Japanese utility-patent publication (Jitsu-Ko-Hei) 3-37055 and Japanese utility-patent publication (Toku-Kai-Hei)7-105781. At the time of adhering the touch panel of plastic substrate to the liquid crystal display panel using the transparent double-sided cohesive sheet, curves may be produced on both the panels in consequence of application of heat and elapsed time, which may further cause the transparent cohesive sheet to be peeled off from the liquid crystal display panel or touch panel. Such cohesive sheet being peeled off from both the panels arises due to a reduction in the adhesive strength due to decreasing the viscosity to restrain the generation of irregularities of the colors on the liquid crystal display surface by pushing and pressing from the surface of touch panel, using a cohesive sheet without a base material in order to raise the degree of transparency.
When the touch panel and the liquid crystal display panel are adhered using the transparent cohesive sheet without base material, raising the adhesive strength to prevent the cohesive sheet being peeled off from the panels causes an increase in hardness of the sheet itself, which largely influences the liquid crystal display screen when pushing and pressing the touch panel.